Fast charging of a smartphone: why it gradually kills the battery

Modern smartphones charge faster than ever before – 50% in 15 minutes, full charge in half an hour. Convenient? Absolutely. But for this comfort we pay an imperceptible price – accelerated battery aging.

Fast charging technologies, which once seemed like a breakthrough, today raise more and more questions among engineers and users, writes YSTNews.

How fast charging actually works
The essence of fast charging is to increase the current or voltage in order to transfer more energy in a short time.
Conventional charging supplies about 5 V and 2 A, and modern systems (SuperVOOC, TurboCharge, HyperCharge) – up to 20 V and 5–10 A.

Such a load causes intense heating of battery cells, especially lithium-ion cells. And although manufacturers are introducing thermal control and dynamic current regulation, heat remains the main enemy of battery longevity. Experts, including those from ScienceDirect, have repeatedly stated this.

“Every 10°C increase in temperature reduces the battery’s service life by about 20–25%. This is physics that cannot be circumvented by any software trick,” explains electrochemist Pavlo Hnatyuk, a consultant at the Energy Saving Systems Laboratory at KPI.

What happens to a battery during fast charging
Increase in temperature.
Metal electrodes expand, the crystal structure changes, and the electrolyte degrades.

Formation of “lithium dendrites.”
These are microscopic needles that can pierce the separator over time and cause a short circuit.

Capacity loss.
After several hundred cycles, a fast-charging battery can lose up to 15–25% of its capacity faster than a conventional one.

Uneven charge distribution.
The upper layers of the elements heat up more, which makes charging unstable – the smartphone “thinks” that it is charged, but the actual capacity is lower.

Which models are particularly prone to wear and tear
Flagships with powerful adapters (100–200 W) – Xiaomi, Realme, OnePlus.

Gaming smartphones – they have an additional thermal load.

Budget models without high-quality temperature control – often overheat when charging for more than 30 minutes.

How to extend battery life
Experts advise a few simple steps that really work:
Use slow charging if you have time.
For example, charge your smartphone via a laptop USB port or an old 5 V adapter.
Do not keep the phone in a case while charging – this retains heat.
Do not charge to 100% constantly.
The optimal range is 20–80%.
Avoid charging overnight.
Even with a “smart” monitoring system, prolonged connection to the network is harmful.
Do not use the phone while charging.
High load (video, games) doubles the temperature.
Why manufacturers continue to promote fast charging
Firstly, it is a marketing race: users choose a smartphone with a higher charging capacity.
Secondly, most users change their phone every 2–3 years, without having time to feel the full aging of the battery.
However, even manufacturers recognize the limitations. Thus, the technical documentation of Samsung, Apple and Google states that prolonged use of fast charging reduces battery life and is recommended only in emergency cases.